Immunity and COVID

The innate immune system, which is our in-born immunity, is our first line of defence against infections caused by pathogens and germs. This innate immunity is very much essential to prevent severe COVID-19 in children. Studies have shown that children have stronger innate immune responses, which is the first-line defence against SARS-CoV-2. They also have a greater number of NK cells. Further, it has been reported that innate immune cells can build immune memory called trained immunity. Trained immunity provides favourable cross-protection from many infectious diseases. After exposure to certain stimuli, including infections and vaccinations, due to the memory build, these trained cells react faster and more actively to subsequent pathogen challenges providing enhanced protection. ^{1,2, 3}

Further, it was observed that children also had more lymphocytes and absolute numbers of T and B cells, which provides a strong T cell-mediated immune response thus protecting children against SARS-CoV-2. Also, studies have shown that children are less prone to pro-inflammatory cytokine a storm, which cause severe COVID-19 complications, ARDS and is responsible for multiorgan failure in critically ill patients ². 

The available data does not provide any significant evidence suggesting that children may be more affected due to COVID-19 infection in the anticipated third wave. Several studies have shown that children have better immunity and milder disease, better prognosis, and low mortality compared to adults ⁴. 

The risk factors to prevent the multisystem inflammatory syndrome (MIS-C) in children include obesity, asthma, compromised breathing, developmental disorders, cardiac disease, cancers or immunocompromised children as well as those who have undergone surgeries.

The emergence of a new delta variant, which has affected children in countries like the UK and Singapore has created fear among the general public that the third wave of COVID-19 may affect children more. But no such significant evidence is yet available, hence is Indian paediatricians are of the view that it is more important to focus on saving children from Covid-19 infection and boosting their innate immunity ⁵.

A Sero-positivity study was carried out by AIIMS (New Delhi) and WHO from March to June 2021 among children of five states. Sero-positivity is the body′s ability to mount a natural immune response to viruses .The study found that seroprevalence was 55.7 % among 2 to 17 years of age, and in 63.5% among age group above 18. The study revealed that children had high sero-positivity which indicate that the third wave of Covid infections may not affect children more than others..^6,7

References

1. https://www.webmd.com/lung/news/20210218/kids-robust-immune-systems-may-shield-from-covid_
2. Zimmermann P, Curtis N, Why is COVID-19 less severe in children? A review of the proposed mechanisms underlying the age-related difference in severity of SARS-CoV-2 infections Archives of Disease in Childhood ,2021;106: 429-439.
3. Helin Tercan , N. P. R., Leo A B Joosten , Mihai G Netea , Siroon Bekkering Trained Immunity: Long-Term Adaptation in Innate Immune Responses, Arterioscler Thromb Vasc Biol ,2020, 41(1), 55-61.
4. https://indianexpress.com/article/india/covid-19-third-wave-children-7356074/
5. https://qz.com/india/2021749/will-indias-third-wave-of-covid-19-affect-more-children/
6. https://www.indiatoday.in/coronavirus-outbreak/story/aiims-study-covid-third-wave-seropositivity-children-antibodies-1816171-2021-06-17
7. https://www.business-standard.com/article/current-affairs/third-wave-of-covid-19-won-t-pose-greater-risk-to-children-study-121061800053_1.html